The study into the effect of NSPs on HIV and HCV, and the consequent return on investment from these programs has reinforced the original findings by Hurley, Jolley and Kaldor. The results demonstrate that NSPs are effective in reducing the incidence of both diseases and that they represent an effective financial investment by government.

From a financial perspective, we have considered only the direct costs of treatment saved by the avoidance of HIV and HCV. Such an approach is inherently conservative, and it is likely that there are further financial benefits derived from the investment in NSPs not included in our findings. As such, the savings we have demonstrated, if anything, understate the total financial benefits to government and members of the community.

When considering the effect of NSPs on the lives of those immediately affected by their operation, namely injecting drug users, the study again demonstrates that NSPs have a positive impact. This has been measured in terms of avoidance of deaths, gains in the duration of life and improvements in the quality of life of injecting drug users. Such benefits are additional to the financial benefits demonstrated.

The study has considered the investment in NSPs during the 1990s, at which time we have assumed that the investment ceased. The consideration of effect has been limited to the future benefits accruing from the cases of HIV and HCV avoided during the investment period. The results demonstrate that, across all measures of effect used in the study, NSPs have yielded a significant public health benefit, and that continued investment is warranted from both a financial and human perspective.